1. Field of the Invention
The present invention relates generally to the field of fluid drop generation and more particularly, to jet drop recording heads of the type disclosed in Lyon et al U.S. Pat. Nos. 3,739,393 and Stoneburner 3,882,508.
2. Prior Art
In recorders of the type referred to above, there are one or more rows of orifices which receive an electrically conductive recording fluid, such as for instance a water base ink, from a pressurized fluid supply manifold and eject the fluid in rows of parallel streams. These recorders accomplish graphic reproduction by selectively charging and deflecting the drops in each of the streams and thereafter depositing at least some of the drops on the moving web of paper.
Substantial investigative effort has been directed to the area of drop stimulation, since this is one of the more difficult and troublesome aspects of the apparatus. Advancements have been made in the art of controlling the uniformity of drops and drop separation by the developments disclosed in the above two referred to patents. The basic construction of the jet drop recording heads disclosed in these two patents comprises an orifice plate of generally thin rectangular construction, a corresponding substantially thicker holder to which the orifice plate is secured, a stimulation device for creating the wave motion in the orifice plate and a reservoir of fluid disposed above the orifice plate for supplying a supply of working fluid to the orifices which is expelled through the orifices in a controlled manner by stimulation of appropriate wave vibration patterns in the orifice plate.
One particular difficulty associated with this arrangement is the occurrence of reflected wave motion along the vibrating surface of the orifice plate, which tends to interfere with the primary wave motion and causes a lack of uniformity in the size of the drops or distance between drops, or produces what is referred to as "satellite" drops which are relatively small droplets that are formed after a large drop has formed.
To alleviate this problem, it has been common in the past to employ a separate acoustical "bumper" at each end of the vibrating portion of the orifice plate and in contact therewith, which absorbs the wave motion at each end of the plate, thus suppressing secondary, backwardly traveling reflections of the primary wave motion. The bumpers are usually formed of a plastic or rubber like material which must be adhered to or formed on the orifice plate within the corresponding openings in the holder.
In the past, the use of such bumpers has proved to be a problem in that after prolonged use the bumpers tend to deteriorate contaminating the inking material, and thus clogging the orifices.